A possible association of hematologic malignancy with hereditary nonpolyposis colon cancer reported in the literature, together with a report that MSH2-deficient mice are susceptible to malignant lymphoma, strongly supports the finding that this patient's lymphoma was related to hereditary nonpolyposis colon cancer.
This phenotype of the brothers is unusual as they neither develop hematological malignancies nor brain tumors at an older age of presentation than other patients with homozygous MSH2 mutations.